1. Field of the Invention
The present invention relates to an internal toothed saw, the internal circumference of which being provided with saw teeth for cutting an object, and more particularly to a versatile internal toothed saw that can be used as a pruning saw, and in particular, as a high-branch-pruning saw for pruning high branches.
2. Prior Art
Among conventional high-branch-pruning saws, manually operated types with saw teeth fastened at the tip of a long supporting stick and electric saws such as chain saws are known.
A type of saw which cuts the object with saw teeth formed on the periphery of a disk is generally known, and a method for cutting the object using a rotating annular internal toothed saw disk is also known as it is disclosed in Japanese Utility Model Application Laid-Open No. S51-88887. But the method for cutting the object using a rotating annular internal toothed saw disk is only used as a precision cutter employing a special thin cutter disk and not as a general saw such as a pruning saw for gardening.
Conventional high-branch-pruning saws, whether manual or electric, are used for cutting branches from a certain direction. Therefore, it is not always possible to cut a given branch accurately depending on the way it grows. For example, if the branch is cut from above, the weight of the branch itself acts on it to open the cut. But this way of cutting is not possible using a conventional high-branch-pruning saw.
Using a conventional annular internal toothed saw disk that rotates, the object is cut by inserting its axial tip inside the internal circumference of the internal toothed saw disk. This is useful when slicing the end surface of the object. However, a conventional annular internal toothed saw disk is not capable of cutting a long object at an arbitrary position.
The object of the present invention is to provide a versatile saw using a rotary internal toothed saw disk that is capable of cutting the object at an arbitrary position. More specifically, the objective of the present invention is to provide a saw such as a high-branch-pruning saw that is capable of cutting a branch from an arbitrary direction, for example, from the top of the branch.
The rotary internal toothed saw of the present invention comprises an openable pair of holders and an annular two-piece internal toothed saw disk that is held by the holders. The openable pair of holders support the periphery of the two-piece internal toothed saw, and are capable of maintaining the annular shape of the internal toothed saw disk with the holders closed. The internal toothed saw disk, which is rotated, is designed to stop at a fixed position with respect to the holders, and at this position, each part of the two-piece internal toothed saw disk is held by the corresponding holder in such a way that they can be opened together with their corresponding holders.
The above configuration makes it possible for the holders supporting the two-piece annular internal toothed saw disk to open and have the object introduced inside the internal toothed saw disk at any position of the object at which the object is required to be cut. When the holders are closed and the internal toothed saw disk is rotated maintaining its annular shape, an object can be cut by the internal teeth of the internal toothed saw disk. The pair of holders which are openable for introducing the object inside the internal toothed saw disk, may be opened by flipping both of them open, but it is also possible to fix one of them and flip open just the other so that the latter opens relative to the former. The holders can also open in any direction, e.g., parallel to the plane, perpendicular to the plane, etc. The important thing is that the object can be introduced inside the internal toothed saw disk.
As a way of introducing the object inside the annular internal toothed saw disk, the internal toothed saw disk may be cut at one place and supported by a holder which is at least divided at one point along its periphery, wherein the internal toothed saw disk is rotated with its annulus maintained in a planar condition and is stopped at the position where the divided position of the holder and the cut position of the internal toothed saw disk meet, and both parts of the holder move in relatively different directions that are each perpendicular to the plane of the internal toothed saw disk to allow the cut part of the internal toothed saw disk to open.
It is also possible to hold the periphery of an annular internal toothed saw disk, which is cut at one place, by means of a holder, which is divided into several parts, wherein some of the several parts of the divided holder hold the internal toothed saw disk and some of the parts of the divided holder are openable so that the internal toothed saw disk can be exposed, and at the cut position of the exposed internal saw disk the cut part can be opened by forces acting in directions perpendicular to the plane of the internal toothed saw disk.